1. Field of the Invention
The present invention relates to a high-performance non-aqueous secondary battery which has a high energy density, a good reversibility between charging and discharging, a very low self-discharge ratio and an excellent thermal stability.
2. Description of the Related Art
A so-called polymer battery comprising an electrode composed of a polymeric compound having a conjugated double bond in the main chain is regarded as a secondary battery having a high energy density. Various reports concerning secondary batteries have been published, for example, by P. J. Nigrey et al, J. Chem. Soc. Chem. Commun., 1979, 594, J. Electrochem. Soc., 1981, 1651, and Japanese Unexamined Patent Publications No. 56-136,469, No. 57-121,168, No. 59-3,870, No. 59-3,872, No. 59-3,873, No. 59-196,566, No. 59-196,573, No. 59-203,368 and No. 59-203,369.
The use of polyaniline obtained by electrolytic oxidative polymerization of aniline, which is a kind of conjugated polymer, as an electrode of an aqueous solution type or non-aqueous solvent type battery has already been proposed [A. G. MacDiarmid et al, Polymer Preprints, 25, NO. 2, 248 (1984), Sasaki et al, Lectures at 50th General Meeting of Electrochemical Association, 123 (1983) and Sasaki et al, Lectures at 51st General Meeting of Electrochemical Association, 228 (1984)].
A polymer of aniline or an aniline derivative is generally prepared by electrochemical polymerization or chemical polymerization. In each case, since polymerization is carried out by oxidative reaction, the process is called an "oxidative polymerization process", and a polymer of aniline or an aniline derivative obtained according to this process is protonated by a protonic acid. Moreover, the polymer is obtained in the state doped with dopant in an amount of several to scores of mole % based on the repeating units.
In order to use a polymer of aniline or an aniline derivative obtained according to this process as an active electrode material, the obtained polymer is dried under a reduced pressure, the polymer is washed with water to remove impurities and then dried under a reduced pressure, or the polymer is washed with an organic solvent. These methods can be used in combination.
In a non-aqueous secondary battery in which a polymer of aniline or an aniline derivative prepared by the above-mentioned oxidative polymerization process and treated by the above-mentioned method is used as the positive electrode and an alkali metal, an alkali metal alloy, an electroconductive polymer, an electroconductive polymer composite is used as the negative electrode, a good battery performance such as a low self-discharge ratio or a high energy density is difficult to obtain, and the characteristics of this secondary battery cannot be regarded as epoch-making and excellent over those of a known nickel/cadmium battery or lead battery.